PCBA Tech - What to do PCBA OEM processing board is short-circuited?

What to do if Shenzhen PCBA OEM processing board is short-circuited?
PCB A board short circuit is a very common problem in the electronic processing industry, usually after handling it, it will not affect the normal use:

1. Short circuit caused by running tin:

1. Improper operation in the de-filming medicine tank causes tin running;

2. The sheets that have been film-relieved are superimposed on each other to cause the tin to run out.

Improve methods:

1. The concentration of the film removal solution is high, the film removal time is long, the anti-coating film has already fallen off, but the board is still immersed in the strong alkali solution, part of the tin powder is attached to the surface of the copper foil, and there is a thin layer of metal tin for protection during etching The copper surface plays a role of anti-corrosion, causing the copper to be removed not to be cleaned, resulting in a short circuit of the circuit. Therefore, we need to strictly control the concentration, temperature, and time of the film removal syrup. At the same time, use the plug-in rack to insert the film when removing the film, and the plates cannot be stacked and touched together.

2. The stripped plates are stacked together before being dried, so that the tin between the plates is immersed in the unbaked stripping solution, part of the tin layer will dissolve and attach to the surface of the copper foil, and there will be a layer during etching The very thin metal tin protects the copper surface and plays a role of anti-corrosion, causing the copper to be removed not to be cleaned, resulting in a short circuit.

3. Short circuit caused by impure etching:

1. The quality of the etching potion parameter control directly affects the etching quality. The specific analysis is as follows:

(1) PH value: control between 8.3~8.8. If the PH value is low, the solution will become viscous, the color will be white, and the corrosion rate will decrease. This situation is easy to cause side corrosion, mainly by adding ammonia Control the PH value.

(2) Chloride ion: controlled between 90~210g/L, mainly through the etching salt to control the chloride ion content, which is composed of ammonium chloride and supplements.

(3) Specific gravity: Control the relative gravity mainly by controlling the content of copper ions. Generally, the content of copper ions is controlled between 145 and 155g/L, and the test is performed every hour or so to ensure the stability of the specific gravity.

(4) Temperature: Control at 48~52 degree Celsius. If the temperature is high, the ammonia volatilizes quickly, which will cause the pH value to be unstable, and most of the cylinder of the etching machine is made of PVC material, and the temperature resistance limit of PVC is 55 degree Celsius, exceeding this temperature will easily cause the cylinder body to deform and even cause the etching machine to be scrapped. Therefore, an automatic temperature controller must be installed to effectively monitor the temperature to ensure that it is within the control range.

(5) Speed: Generally adjust the appropriate speed according to the thickness of the bottom copper of the plate. Suggestion: In order to achieve the stability and balance of the above parameters, it is recommended to configure an automatic feeder to control the chemical components of the sub-liquid, so that the composition of the etching liquid is in a relatively stable state.

2. The thickness of the electroplating layer is uneven when the whole plate is electroplated copper, which causes the etching to be unclean. Improve methods:

(1) When electroplating the whole plate, try to realize automatic line production. At the same time, adjust the current density per unit area (1.5~2.0A/dm2) according to the size of the hole area, and keep the electroplating time as consistent as possible. For the cathode and anode baffles, the use system of "plating edge strips" is formulated to reduce the potential difference.

(2) If the full-plate electroplating is manual line production, double-clamp electroplating is required for large plates, try to keep the current density per unit area consistent, and install a timing alarm to ensure the consistency of the plating time and reduce the potential difference.

After dealing with the defective PCBA board in Shenzhen with short circuit, it should be sent to the testing department for testing according to the requirements, and can be distributed to the market after being approved by the quality department.